[ntp:questions] How does NTP calculate peer accuracy?

singha singh.arvinder at gmail.com
Mon May 5 20:16:02 UTC 2008


I have seen a similar description in many website and even a couple
books. The text in this question was taken from "http://
networking.ringofsaturn.com/Protocols/ntp.php".

While I'm at it I'll describe my setup as well. I have two equivalent
machines (A & B) which I want to be tightly time synchronized with
each other. Both machines will have the same reliable external servers
configured in the NTP config file. But I want to be covered in the
case that the machines lose connectivity to the external NTP servers.

This is what I understand after looking at all the responses:
- My assumption that setting Machines A & B as NTP peers still seems
to be a good setup.
- Losing connectivity to the reliable time sources from all peers is
called Orphan Mode
- I'll call the case when the time sources are available as Normal
Mode
- In Normal Mode the machines will set their time based on a logical
weighted average of its external source and its peer.
- In orphaned mode the two machines will pick one of the machines as
server based on some mysterious NTP random number.

Do the assumptions above sound correct?
In orphan mode say if machine A is chosen as the NTP master would A
sync to itself and not B? Or do both A and B become Master and Slave
of each other and use a weighted average of the local machine an
peer?
Is peering the best option in my case?

Thanks for all your help!




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